Cedars-Sinai neurosurgeons are using lasers to treat mesial temporal lobe epilepsy and ablate tumors located deep inside the brain.
Adam N. Mamelak, MD
"The basic idea is to destroy a particular structure in the brain in a controlled fashion, and in a very minimally invasive way," said neurosurgeon Adam Mamelak, MD. "Instead of opening up the brain and cutting something out, you’re making a 2- to 3-millimeter hole, passing a probe to that area and ablating the tissue.”
The FDA-approved technique, called MRI-guided laser interstitial thermal therapy (MRgLITT), has been used in the liver and elsewhere in the body for many years. For patients with uncontrolled seizures, laser ablation is used principally in the amygdala and hippocampus, but can be used throughout the brain to destroy the onset spot (focus) of seizures.
At Cedars-Sinai, laser ablation can be life-changing for patients suffering from mesial temporal lobe epilepsy. The procedure can also address radiation necrosis and can provide therapy to patients with certain malignant brain tumors.
"The number one goal is to make someone fully seizure-free. In those patients, we often hear amazing stories of people resuming the life they had prior to epilepsy."
How laser ablation works
To perform laser ablation, the surgeon first inserts a probe into the brain using a small hole. The insertion point and trajectory of the probe are carefully planned to ensure that the area to be treated will be accurately targeted. This is done using sophisticated planning software and a robotic system to ensure submillimeter accuracy. Once placed, an MRI confirms the location of the probe. MRI thermography, a technique that measures the temperature of the brain and visually displays this on an MRI, measures the exact temperature of the tissue to determine where and how long to activate the software-controlled laser.
"The combination of being able to monitor the temperature in real time with an MRI, and using lasers that can deliver very focal heat allows the surgeon to burn or destroy a focal area of tissue in a very safe and controlled way," Mamelak said.
Real-time monitoring via MRI imaging shows where tissue is destroyed, stunned or unaffected. The laser ablates a ball of tissue, and the surgeon then backs the probe up and ablates another ball of tissue. The process is repeated, forming "a string of pearls” of destroyed tissue, Mamelak said.
Using lasers for tumors and epilepsy
Malignant brain tumors are difficult to cure with any method, but laser ablation is an effective option for treating brain tumors in a way that avoids opening up the brain and risking complicated side effects.
"The primary advantage is that you can potentially accomplish the same goals in a minimally invasive manner," Mamelak said.
In patients with malignant brain tumors, the procedure is most commonly used when a brain metastasis has failed radiation. The laser can treat any radiation necrosis alongside the metastasis. Laser ablation can be an effective option for tumors located in the thalamus, basal ganglia structures or deep in the brain, where open surgery is typically not available.
In addition to tumors, laser ablation can make a meaningful difference in the lives of patients suffering from epilepsy.
To be a good candidate, patients must have a known seizure focus that can be safely reached with a probe. The surgeon also must be able to ensure the area can be covered by the volume of the ablation.
"If the area is too large, ablation is not a good option. There are limits to how big of an area you can ablate," Mamelak said.
Laser ablation is often appropriate for patients with mesial temporal lobe epilepsy, the most common form of focal epilepsy involving the amygdala and the hippocampus. Focal cortical dysplasia and hypothalamic hamartoma can also both be addressed with laser therapy due to the location and size of the seizure focus.
Comparing laser ablation with traditional methods: risks and limitations
For some patients with temporal lobe epilepsy, medical management alone does not fully address seizures. Traditional surgical options, either temporal lobectomy or an amygdalohippocampectomy, both require a craniotomy and brain retraction.
Laser ablation is a minimally invasive way to target the same tissues. With only a stab incision, the patient can return home the next day. The surgeon’s laser cannot burn a blood vessel or structures outside the area.
"As soon as the laser’s heat reaches either a blood vessel or fluid, the heat is dissipated immediately," Mamelak said. "That adds a tremendous amount of safety for the procedure."
The procedure does have its own challenges. With MRI image guidance, the surgeon cannot physically look at where the probe is inserted. The surgeon can hit a blood vessel without knowing it. As with a traditional method, bleeding and hemorrhages are possible, and in the minimally invasive setting, it can be difficult to control bleeding.
The innovative procedure is offered at Cedars-Sinai and at a handful of other tertiary and quaternary centers across the country. While the procedure is FDA-approved, current research tends to include smaller, institutional-based studies or long-term follow-up studies to analyze overall seizure control rates and determine the long-term efficacy of the procedure compared to traditional methods.
Patients can become seizure-free
Epilepsy can have dramatic impacts on patients’ work, family, social and romantic lives. Mamelak has observed the life-changing impact laser ablation has had on the lives of patients with mesial temporal lobe epilepsy—some patients have even become seizure-free following the procedure. One of his patients dealt with seizures for two decades.
"She was hesitant to have surgery, but her seizures caused real disability. She had no independence and couldn’t work," Mamelak said. "Finally, she had surgery and became seizure-free within a year. She got a job she loves, started taking care of her father, got engaged and is absolutely a different human being."
Mamelak acknowledges that surgery can be scary for patients, but encourages physicians to be vocal in advocating for surgery when it is an appropriate and beneficial option.
"In patients that are cured, the impact is dramatic," Mamelak said. "The number one goal is to make someone fully seizure-free. In those patients, we often hear amazing stories of people resuming the life they had prior to epilepsy."
